Deposition of single or multiple layers on substrates from dilute gas sweep to produce optical components, electro-optical components, and the like

ABSTRACT

A very thin layer is deposited from a dilute gas sweep onto suitable substrates including glass, metal, plastic, etc., in an atmospheric pressure process. Moderate temperatures, i.e., between 100*C and 300*C, can be used, although higher temperatures are sometimes useful. For example, in a preferred embodiment for manufacturing a multiple layer optical component, e.g., a dichroic filter, relatively small amounts of gaseous deposition precursors or reactants are thoroughly admixed in a large volume of high velocity gas stream to provide a relatively dilute, gas-vapor deposition stream. To produce alternating layers, two different dilute high velocity gas streams are alternately introduced into a relatively large atmospheric pressure coating chamber containing a plurality of substrates, which substrates are preheated to a deposition temperature of about 200*C.

United States Patent 1191 Stelter Apr. 30, 1974 DEPOSITION OF SINGLE ORMULTIPLE LAYERS ON SUBSTRATES FROM DILUTE GAS SWEEP TO PRODUCE OPTICALPrimary Examiner-Ralph S. Kendall Assistant Examiner-Michael EspositoAttorney, Agent, or Firm-Greist, Lockwood, Green- COMPONENTS,ELECTRO-OPTICAL Walt & Dewey COMPONENTS, AND THE LIKE Inventor: ManfredK. Stelter, 605 Waukegan [57] ABSTRACT Rd., Glenview, [11. 60025 Filed:Dec. 9, 1970 Appl. No.: 96,428

A very thin layer is deposited from a dilute gas sweep onto suitablesubstrates including glass, metal, plastic, etc., in an atmosphericpressure process. Moderate temperatures, i.e., between 100C and 300C,can be used, although higher temperatures are sometimes US. Cl. 117/106R, 117/106 A, 117/333 useful. For example, in a preferred embodiment forInt. Cl. C23c 11/00, B29d 1l/00 manufacturing a multiple layer opticalcomponent, Field of Search... 1 17/ 106, 33.3, 106 R, 106 A e.g., adichroic filter, relatively small amounts of gaseous depositionprecursors or reactants are thoroughly [56] References Cited admixed ina large volume of high velocity gas stream UNITED STATES PATENTS toprovide a relatively dilute, gas-vapor deposition 2,831,780 4/1958Deyrup 117/106 x i To poduce alternating layers different 3,306,7682/1967 Peterson 7/106 R d1lute high velocity gas streams are alternatelyintro- 3161 11813 12/1961 Lely et al.... 117/106 R duced into arelatively large atmospheric Pressure 3,031,200 3 19 3 T0mpkin 117 10 xcoating chamber containing a plurality of substrates, 3,142,586 7/1964Colman 117/106 R which substrates are preheated to a deposition tem-2,847,330 8/1958 Toulmin 7/1072 R perature of about 200C, 3,032,3975/1962 Niederhauser 117/106 X 19 Claims, 4 Drawing Figures.PATENTEBAPHOM 3.808035 sum 1 or z 2 so 0 6 60 2 (D 1 0: 40

WAVELENGTH. 1N MICRONS INVENTOR MANFRED .K. STELTER ATT TPATENTEDAPR 30I974 SHEET 2 (1F 2 MANFRED K. STELTER 0HHHHHHHHHHHHH INVEN TORDEPOSITION OF SINGLE OR MULTIPLE LAYERS ON SUBSTRATES FROM DILUTE GASSWEEP TO PRODUCE OPTICAL COMPONENTS, ELECTRO-OPTICAL COMPONENTS, AND THELIKE This invention relates to a method and apparatus for producingoptically or electro-optically active layers, and the like, e.g.,dichroic filters of the type comprising an optical substrate havingmultiple micro-thin layers of optical filter material thereon.

These layered products are presently well known in the art and theindustrial, commercial and scientific value of these products is wellestablished.

One of the shortcomings of some of the specific methods heretoforeavailable for the manufacture of these layered products is the extremelyhigh vacuum environment which is required in these specific methods.Other previously suggested practice requires the use of expensive orsophisticated electronic equipment such as that associated with electronbeam evaporation, glow discharge cleaning or RF-sputtering tomanufacture corresponding optical filters.

Another shortcoming of some of the methods heretofore available for themanufacture of such layered products is the extremely high temperaturesrequired in these methods, i.e., temperatures at or above the softeningpoint of a glass substrate, for example. While such methods may beuseful for coating glass sheets, etc., they are not suitable for use tocoat pre-shaped substrates, e.g., lenses, glass flats and the like, dueto the greater likelihood of distortion and shape-change, which becomesmore likely to occur at softening temperatures, and at highertemperature. This distortion effect is also detrimental if parts have tobe coated which contain highly accurate graduations or indicia forprecision measurements. Here already temperatures above 250 C can causeirreparable damage. Moreover, methods requiring very high temperatures,e.g., above 500C do not lendthemselves for use with most pla'sticsubstrates.

Similar layer forming techniques have been suggested for use to depositelectro optical components, e.g., layers for photocells, or photoreadout gratings. High vacuum thin film deposition, and extremely hightemperature epitaxial techniques were suggested. Also, in conjunctionwith such methods, mechanical masks or photo-resist stencils were usedfor pattern generation for selective deposition.

Some heretofore suggested methods involved vapor deposition fromatmosphere rich in the deposited material, or rich in a precursor, orreactant which results in or yields a material constituting theresulting layer. These methods are considered to be deficient because ofthe difficulty in depositing a large number of high qualitysubstantially equal coatings simultaneously. The deficiency is believedto be the result of localized differences in availability of reactantsand, at least in part, because of chemical interference at the substratewhich is occasioned by what I now believe to be excessive quantity ofreactants.

Another shortcoming of many heretofore available methods ofmanufacturing such optical filters and electro-optical layers relates tolayer quality, and is believed to result from the so-called line ofsight nature of deposition transfer achieved in many high vacuummethods. This results in difficulty in achieving a uniform layerreqardless of the shape of the substrate, e.g., on a concave or convexface as well as on an irregularly shaped substrate, being impinged bythe layer-forming material during high vacuum methods, e.g., in electronbombardment-vapor deposition. For example, one difficulty associatedwith such coating methods is the tendency for the coating to beincomplete due to the presence of voids. These voids are believed to becaused by the shadow of minute surface irregularities. Sinceirregularities shade the regions immediately behind themselves fromcoating material traveling in a straight line from the source, minuteprojecting irregularities are found to build up and the shadows behindthem are found to be deficient in, if not devoid of, layer material.

Another deficiency to the high vacuum, line-of-sight methods ofdeposition is the difficulty in uniformly coating irregularly shapedarticles, and the difficulty in simultaneously uniformly coating a largenumber of substrates.

It is an object of this invention to provide a method and an apparatusfor manufacture of single or multiple layer optical components andelectro-optical components, and the like, which method does not requirehigh vacuum conditions. It is a further object of this invention toprovide a method of manufacture of optical filters such as dichroicfilters, which method does not require the use of extremely hightemperatures or the use of very sophisticated electrical or electronicequipment such as that involved in electron beam deposition andbombardment.

It is an additional object to provide a method of manufacturing singleor multiple layer products which lends itself to multiple unitprocessing wherein a large number of filters or other components aresimultaneously produced with great uniformity.

It is an additional object to provide a method for depositingmicro-miniature patterned layers and other miniature pattern layers. Itis another object to provide a method for depositing layers whichpermits great control over the extent and makeup of a transition layer.

It is a further object to provide a simple and reliable method forproducing high quality uniform continuous optical filter layersregardless of shape of the substrate, and regardless of the presence ofminute projecting irregularities on the substrate.

These and other objects which will be apparent hereinafter are allachieved in accordance with this invention as set forth in the followingdisclosure, wherein:

FIG. 1 illustrates a dichroic filter coated optical lens shown in sideelevational view;

FIG. 2 is a greatly enlarged elevational cross sectional view takenapproximately along the line 22 of FIG. 1;

FIG. 3 is a graph showing percent transmission versus wavelength, whichgraph illustrates the optical property of the dichroic filter shown inFIGS. 1 and 2; and

FIG. 4 is a schematicdiagram of a preferred apparatus for use inaccordance with the invention.

In the figures the numeral 10 refers to an optical lens having multiplelayers generally 12 of dichroic filter deposited on the convex surface14 thereof. The layers 12 were deposited in accordance with the methodof this invention, and specifically, in accordance with the preferredembodiment described hereinafter in the example. The filter segmentillustrated in FIG. 2 includes a glass substrate 16 which is providedwith a first coating 18 of iron oxide, a second layer 20 comprisingchromium oxide, a third layer 22 comprising iron oxide, a fourth layer24 comprising chromium oxide and an outer layer 26 comprising ironoxide. In the illustrated segment a rather sharp interface 28 is shownbetween glass substrate 16 and layer 18. However, transition zone 30occurs between layer 18 and 20, and transition zones 32, 34, 36 occurrespectively between layers 20, and 22, 22 and 24, and 24 and 26. Thesetransition zones represent relatively narrow transition in which thezone has decreasing concentration of the inner layer material andincreasing concentration of the nextouter material at points increasingin distance from the substrate.

The coated lens of FIG. 1 and FIG. 2 has optical properties illustratedin the graph of FIG. 3. It is noted that the percent transmission oflight having wavelengths greater than 0.7 is virtually constant at about8 percent. However, percent transmission of light at wavelengths lessthan 0.4 is substantially zero.

The method and apparatus of this invention is extremely simple andreliable and, in the following discussion, the apparatus will first bedescribed briefly and the method will be described by means of theillustra tive example and subsequent general discussion.

A preferred embodiment of the apparatus of this invention which isschematically illustrated in FIG. 4 includes a number of gas-tighthermetically joined elements. Vaporizers 40, 42, in this embodiment,have an internal volume of about one pint. Vaporizers 40, 42 are heatedby heating means 44, 46 respectively, which are diagrammaticallyillustrated by resistance coils. Any convenient, compatible method of,and apparatus for, heating vaporizers 40, 42 can be used. It is mostdesirable that heating means 44, 46 include means for automaticallytemperature-regulating vaporizers 40, 42. Either or both vaporizers 40,42 can be supplied with a stream of helium or other inert gas throughmanifold 50 and conduits 52, 54, respectively. Elements 53, 55,respectively, indicate supply and metering system by which respectivevolatile (or gaseous) reactant meterial is charged to vaporizer mixers40, and 42, respectively. For extremely precise control of vaporizeroutput rate, it is preferred to operate vaporizers practically dry, withsweep passing through, with the volatile liquid, being continuouslyadded by means of a conventional constant advance piston, preferably onedriven by a geared-down variable speed electric motor in a conventionalmanner. Elements 56, 58 schematically represent gas flow measuring andcontrol devices.

Although, in the diagram, vaporizer flow is shown passing throughsubmerged porous plates 59, 59', any conventional means for intimatelycontacting vaporizer sweep gas with vaporizing material can be used,e.g., a submerged inlet, fritted plate, etc.

Conduits 60, 62 carry effluent gas mixture from vaporizers 40, 42respectively, to a second manifold 64. Valves 66, 68 provide on-off flowcontrol from respective vaporizers 40, 42 to manifold 64. Devices 69, 69are intended schematically to illustrate vented pressure-relief safetyvalves. Manifold 64 receives conduits 70, 72, and 74 for supplyingreactant or sweep gases, e.g., CO 0 and N respectively. Elementsdesignated as 76, 78, and 80 are intended schematically to indicate flowmeasuring and control devices for measuring and controlling respectivegas flow in conduits 70, 72 and 74, respectively. Conduit 74 receives agas stream from manifold 82. Manifold 82 also supplies conduit 84 whichis equipped with on-off valve 86.

Manifold 64 empties into mix chamber which has a relatively largevolume, about 1 gallon, and preferably includes a number of baffles 92.Mix chamber 90 is equipped with temperature regulating heating means 94,which temperature regulating device is diagrammatically illustrated. Mixchamber effluent is carried by way of conduit 96 from chamber 90, paston-off valve 98 into conduit 99 which is hermetically joined to coatingchamber 100.

The temperature of the dilute gas stream being conveyed to chamber 100is maintained below the deposition temperature, and below a temperatureat which chemical reaction in the vapor phase is significant.

Coating chamber 100 is of relatively large volume, about four cubic feetincluding the volume of contents, and includes supports 102, 104 forsupporting a plurality of lenses 10. In the illustrated embodiment,supports 102, 104 are shown highly perforated to facilitate gas movementaround lenses 10. Elements 102, 104 are intended to schematicallyillustrate either supports or separators each of which is carrying alayer of lenses 10. It is noted that'a first layer of lenses 10 issupported on element 102 and a separate layer of lenses is supported onelement 104. It is also noted that lenses 10 are separated from oneanother horizontally, as well, to provide ready access of the gas phasein chamber 100 to the faces of lenses 10. Chamber 100 vents throughvented exit conduit 106 and the flow through exit 106 can be regulatedby valve 108. Lenses 10 in chamber 100 are maintained at substantiallyconstant temperature, e.g., 200C, by heater 110. The heater can be ahigh resistance type heater, microwave or similar heater.

Mechanical pump 112 can be used to facilitate flow through coatingchamber 100, and to provide the necessary pressure increase to recycle aportion or substantially all of the gas stream through recycle line 116back through the system. Element 114 represents a conventional liquidnitrogen trap for freezing substantially all of the condensibles out ofthe recycled stream.

Cooling means 120 schematically indicated as a coiled water-cooledtubing is provided to keep conduit 99 from being excessively heated dueto conduction from chamber 100. Appearance of smoke emitting fromconduit 99 indicates temperature of the gas stream is too high, and heatinput must be reduced upstream.

EXAMPLE I To illustrate the simultaneous manufacture of a large quantityof glass filters with a band pass in the visible but strong absorptionin the ultraviolet range of the spectrum, (e.g., filters used forsunglasses) the following procedure is used in accordance with thisinvention:

Cleaning of Lens The lens is cleaned in strong acid, e.g., concentratedsulfuric, nitric, or the like, to remove all possible organic andinorganic contaminants. This acid treatment is followed by a water rinseand a neutralizing step. To neutralize, the glass is immersed in asolution of ammonium hydroxide and hydrogen peroxide. A second waterrinse follows, and the glass is dried in a solvent mixture that absorbswater clinging to the glass and allows flash drying Without residue. Apreferred drying mixture is a mixture of ethanol, methanol, isoamylacetate, and isobutanol in the ratio of 5:l:0.5:0.4. After drying theglass is ready for deposition.

Deposition The thus cleaned glass is transferred to supports 102, 104 inchamber 100 using care not to re-contaminate the surface to be coated,and is then heated to 200C. The process is started by flushing thesystem comprising manifold 82, conduit 80, 84, manifold 86, mix chamber90, conduit 99, chamber 100 and vent 106 with a nitrogen sweep. However,any other inert gas such as helium, neon, or other noble gases can beused for the sweep. It is preferable that lines leading to and comingfrom vaporizers 40, 42 likewise be swept with an inert gas at theinitial stage of the method. After the initial sweep is completed valves86, 80 are closed, thus interrupting the flow of nitrogen. Valve 76 isopened and adjusted to provide a flow rate of 5,000 ml/min of carbondioxide. Valve 78 is regulated to provide a flow rate of oxygen of 5ml/min into manifold 64. Vaporizer 40 is charged with ironamyl-acetonate and is heated to elevated temperature somewhat below theatmospheric pressure boiling point of iron-amyl-acetonate. Vaporizer 40is then swept with helium admitted from manifold 50 through conduit 52at a flow of 5,000 ml/min regulated by adjustment of flow measuring andcontrolling device 56. Hence, the carbon dioxide, oxygen, and the heliumcarrying gaseous iron amyl-acetonate are thoroughly mixed in manifold 64and in mix chamber 90. In mix chamber 90 the turbulent serpentine flowof the mixture through the tortuous path defined by baffle 92 not onlythoroughly mixes the gas but assures thermal equilibrium as well. Theresultant gas mixture is carried through conduits 96, 99 into reactionor deposition chamber 100. Thus in chamber 100 the concentration ofinert sweep gas gradually decreases as additional quantities of thefirst deposition mixture heretofore described is admitted thereto.Conversely, the concentration of the deposition mixture in chamber 100gradually increases as more and more of the initial inert sweep gas isvented. The glass substrates are maintained at approximately 200Cthroughout the deposition. During the ensuing period of time, a highestquality uniform coating of iron oxide forms on the exposed surfaces ofsubstrate 10. I do not want to be bound by any theories as to thechemical mechanism by which the coating is formed in the method of thisinvention.

After lapse of a predetermined time, valves 56, 66 are closed and valves68, 58 are opened. Valve 58 is adjusted to regulate the sweep flowthrough vaporizer 42 at about 5,000 ml/min. Vaporizer 42 had beenpreviously charged .with chromium carbonyl and is maintained at atemperature somewhat below the boiling point of chromium carbonyl.Because of the high volume sweep rate, vaporizers 40, 42 are maintainedat a temperature below the atmospheric pressure boiling point of thematerial being vaporized.

Thus, the primary chromium carbonyl-containing helium stream nowentering manifold 64 through conduit 62 is likewise mixed with thesecondary carbon dioxide-oxygen stream which is maintained at theconstant flow levels defined above, and the primary and secondarystreams are thoroughly mixed and the temperature is equilibrated inmixing chamber 90. The mixture resulting from the primary and secondarystreams may be considered to be a tertiary stream containing chromiumcarbonyl and oxygen in low level. The concentration of the ironamyl-acetonate in the gas in manifold 64 and mix chamber 70 abruptlydrops and the concentration of chromium carbonyl in manifold 64 and mixchamber 90 abruptly increases to its equilibrium level. The chromiumcarbonyl-containing tertiary gas stream is conveyed through conduit 99into largevolume deposition chamber 100. It will be appreciated that theconcentration of iron amyl-acetonate in the reaction chamber 100 willdecline gradually, relatively speaking, as the concentration of chromiumcarbonyl in the reaction chamber 100 gradually increases to itsequilibrium level, i.e., about the concentration in the tertiary stream.The deposition of the respective films on respective substrates 10during this relatively short period of time in which a mixture of ironamylacetonate and chromium carbonyl is available results in the presenceof transition zones 30, 32, 34 and 36. At this stage of the methoddescribed immediately hereinbefore, the period of time during which ironamylacetonate concentration in chamber 100 is decreasing and in whichthe concentration of chromium carbonyl in chamber 100 is increasingdepends primarily on gas flow rates, since the volume of chamber 100 isconstant. This reliably results in the formation of a uniform zone 30between layers 18-20 in separate runs, provided gas flow rates andtemperatures are the same in each separate run. When the ironacetylacetonate is swept out of chamber 100 and chromium carbonylreaches equilibrium concentration, a layer which is substantiallychromium oxide is deposited. After lapse of another predetermined periodof time, during which a high quality chromium oxide layer is deposited,-

valves 68, 58 are closed. Valves 56, 66 are immediately reopened and theflow of helium through vaporizer 40 is regulated to again provide 5,000m./min. The concentration of chromium carbonyl in manifold 64 and mixervery abruptly drops to substantially zero, and the concentration of ironamyl-acetonate very abruptly increases to substantially its equilibriumlevel. At this stage of the method, the primary gas stream againcontains iron acetyl acetonate, the secondary gas stream still containsa low level of oxygen, and the tertiary stream leaving mixer 90 is ahomogeneous mixture of the two streams. However, when the new ironamylacetonate carrying tertiary stream is discharged into chamber 100,there is again a relatively gradual increase in the concentration ofiron amyl-acetonate concentration, and the chromium carbonylconcentration gradually decreases. At this stage in time in which theatmosphere of chamber provides both iron amylacetonate and chromiumcarbonyl, the second transition zone 32 between layers 20, 22 is beingformed.

The above procedure in which the gas streams are alternately routedthrough vaporizers 42, and 40 are repeated to provide a total number offive layersthree of which are iron oxide and two of which are chromiumoxide, each having relatively narrow transition zones therebetween, wascarried out in a total time of less than 1 hour. All the lenses inchamber 100 were identically and uniformly coated.

The procedure described in Example I hereinbefore includes a highvelocity sweeps passing through the vaporizers. It is not essential thatsuch a sweep pass through the vaporizer in accordance with thisinvention. It is essential however that the volatile reactant bethoroughly admixed and diluted with the inert carrier stream prior tocontacting the substrate. Thus, for example, introduction of purevolatile reactant directly into a large volume gas stream passingthrough manifold 64 is within the concept of this invention, althoughsuch operation is not most preferred. Also, it is apparent to oneskilled in the art, that heat is not essential in the vaporizer, in allinstances. However, for ease of control and reproducibility, it ispreferred that the vaporizer be operated at sufficiently hightemperature for it to be maintained in a substantially dry conditionwith a relatively high velocity gas through-put while liquid volatilereactant is being continuously charged thereto at the required constant,although relatively slow, rate of addition.

It is essential in accordance with the present invention that the totalconcentration of the reactants in the inert carrier gas stream be belowpercent volume/- volume. It is more preferred that the concentration ofthe reactants in the carrier gas stream be less than 1 percent v/v, anduse of concentrations of individual reactants at less than 0.1 percentv/v is most preferred. Though it may appear to be inefficient to providethe coating material at these low concentrations in the gas phase, atleast in terms of mass-transfer, I now appreciate that use of the lowconcentration reactant streams in accordance with this inventionprovides layer uniformity and quality which was heretofore unattainable.This is particularly significant in deposition chambers in which a largenumber of substrates are being coated simultaneously, or in which alarge number of substrates are being treated simultaneously to providereproducible and substantially identical layers, particularly in fine ormicro-miniature patterns. By not permitting the relatively dilutereactant carrier gas to stagnate, and by providing positive sweep of thecarrier gas over the substrates, extremely uniform, high quality layersare deposited. While 1 do not want to be bound by any theories as to themechanism involved, it is my belief, based on repeated observation, thatone of the factors responsible for the high quality and high uniformityof the product of this invention is the fact that with the dilute gasstreams, localized variations in vapor phase composition is, relativelyspeaking, eliminated as a source or cause for nonuniform layerdeposition, and undesirable vapor phase reaction is virtuallyeliminated. While 1 do not want to be bound by any particular theory asto why my method works so well, I recognize the possibility that thereactions take place exclusively in an adsorbed phase on the surface ofthe substrate in my method. It is noted that even at the most preferredconcentrations, e.g., less than 1 percent v/v of the reactants or less,more than adequate masstransfer is provided by supplying the dilutesweep in high velocity.

The foregoing example is for illustrative purposes only and is notintended to suggest any limit to the identity of the sweep gasesorreactant compounds which are useful in accordance with this invention.Any metal-eontaining vaporizable material can be charged to vaporizers40, 42, providing that material decomposes or deposits on the hotsubstrate surface a desired layer composition. Indeed, the number ofvaporizers used and the number of kinds of layers can be greater thanthe two which are illustrated in the example. A larger number ofcompositions can be conveniently deposited as an optical filter. inaccordance with this invention.

Other volatile material which can be used to provide an iron oxide layerinclude any of the volatile iron organo-metallic compounds, for example,iron pentacarbonyl, when used in conjunction with oxygen in the secondsweep stream. Likewise, any volatile chromium compound can be used invaporizer 42, for example, chromyl chloride. Thus, it is not necessary,in accordance with this invention, to limit the compounds utilized toorgano-metallic compounds since the compounds which are used can beeither organo-metallic or inorganic. The metallic compounds employed inthis invention are those which exhibit a substantial vapor pressure,preferably in excess of about 40 mm Hg. at

relatively low temperatures, e.g., 200C. However, compounds having lowervapor pressures are also useful, e.g., silver formate has a low vaporpressure at 200C, and such compound is useful for doping films in thevapor phase method of this invention. Procedures for doping will bediscussed in greater detail hereinafter. The secondary carrier gas neednot be limited to the carbon dioxide disclosed in the example but can benitrogen, oxygen, H 0 or similar gases. Oxygen is used only in very lowlevels and only when an oxide coating is desired.

Thus, in the illustrated embodiments, the primary metal-containing gassweep stream is mixed with a secondary gas stream, in accordance withthis invention, which secondary stream includes a low concentrationlevel of a second reactant. The second reactant which was selected toprovide an oxide layer in the illustrated embodiment set forth above isoxygen. However, if it is desired that the deposited layer be a sulfide,selenide, telluride, nitride, arsenide, phosphide, or other desiredcompound, it is only necessary to substitute for the low level of oxygenin the secondary stream a relatively low level of hydrogen sulfide,hydrogen selenide, hydrogen telluride, ammonia, arsine or phosphine,respectively, and the like. Thus, the identity of the material beinglaid down to provide the optical layer can be changed by varying themakeup of the gas stream entering the deposition chamber either byvarying the identity of the material being vaporized in vaporizers 40,42 and the like, or alternatively, in accordance with this invention,the material entering the manifold from the vaporizers, e.g., fromvaporizer 40, can remain constant. in the latter instance the secondreactant, e.g., 0 being mixed with the CO can be eliminated and can bereplaced by similar amounts of a third reactant, e.g., H S, for mixingwith the CO to provide an H S-CO secondary stream. Alternating themakeup of the secondary stream in this manner would provide alternatinglayers of iron oxide and iron sulfide, for example.

It is also contemplated that a doped layer can be deposited using themethod of this invention by adding very low levels of volatileactivator-metallic compounds to either the compound in vaporizer, orinto the secondary reactant gas stream. For example, tetraethyl lead canbe vaporized in a N stream at 5,000 ml/min sweep at 25C vaporizertemperature. The secondary reactant could be H S, at 5 m./min instead ofO Argon would be used instead of CO ln second vaporizer, silver orcopper activator precursor, e.g., copper formate is vaporized in argonor helium at 100C temperature or silver chloride is vaporized at 400C.

In some instances the metal, itself, can be vaporized and diluted inaccordance with the present invention for incorporation into a layer,especially as a dopant. It is also contemplated that an opticalcomponent such as a filter comprising a single deposited optical filterlayer can be deposited in accordance with this invention.

An example of an application of the method of this invention to thedeposition of a layer coating which exhibits a continuous and continualtransition from one density to another density is the use of thisinvention to provide a coating on glass fiber optic fibers. For'example,in accordance with the procedure illustrated in the previously set forthdetailed example, a layer of material having a relatively low index ofrefraction is initially deposited on the glass fiber, and theconcentration of thelayer precursor in the sweep gas phase is graduallydecreased over a relatively long period of time, e.g., a half hour.Simultaneously the concentration of a second layer precursor,-i.e., onewhich provides a layer which exhibits a relatively high index ofrefraction, is gradually increased during the same period of time. Thisprovides a transition zone layer or coating on the glass fiber whichexhibits a low index of refraction of the coating gradually increasingwith increased distance from the fiber through the coating layer. Ifdesired, a mirror layer can be deposited at the outer surface of thethus coated fiber as described herein, also in accordancewith thisinvention. Such coatings improve reflection characteristics andabsorbance to prevent interfere'nce from neighboring fibers.

The method of this invention is also highly useful for depositingopaque, or mirror layers, as well as for depositing transparent layers.For example, in accordance with this invention, an exterior oxide layerof a desired metal is deposited as disclosed herein. The oxide is thenreduced in an oxygen-free atmosphere, e.g., with hydrogen, ammonia,carbon monoxide, or the like, most preferably by introducing thereducing gas into a high velocity stream in low concentration, e.g., atthe ml/min rate in a 10,000 ml/min sweep.

It is preferably to provide an additional oxide layer on top of thereduced metal layer to protect or shield it from atmospheric corrosion.However, osmium or rhodium mirrors do not need an oxide shielding layerdeposited on the top thereof. However, these layers, i.e., osmium orrhodium, are preferably laid down on a foundation layer of an oxide oftin, titanium, chromium, or iron. A preferred over-layer for use on amirror film layer is silicon dioxide. For some mirrors, e.g.,

an iron mirror, flushing with carbon dioxide prior to exposure toatmospheric oxygen passivates the mirror metal for at least temporarycorrosion protection. In the latter case it is not necessary to depositan oxide layer before exposing the metal to atmospheric oxygen.

To employ the method of this invention to manufacture electro-opticalreadout systems and the like such as gratings, a thin film ofphoto-sensitive resist can be applied to a glass substrate cleaned as inExample I. In accordance with well known conventional procedures aphotoresist relief pattern (either positive or negative) is generatedand developed on the substrate, e.g., see Photo Fabrication pamphletsnumbered P. 7 and P. 91 respectively published by Eastman Kodak Company,the contents of which are incorporated herein by reference thereto.Substrates so patterned, are transferred to coating chamber and theflush and layer forming procedure of Example I is repeated to produce adesired layer. After a layer is deposited, the stencil is removed by aconventional procedure.

For transparent gratings or patterns, the preferred layer or layerswhich are deposited is a metal oxide, e.g., an oxide of iron, chromium,cobalt, nickel, uranium, copper, manganese, vanadium, rare earths, lead,etc. For absorption characteristics alone, a single layer can suffice.lf reflection or dichroic characteristics are desired, multiple layersare used, e.g., as illustrated in Example I. For opaque patterns, areactant composition is selected to produce an oxide which is thenreduced by dilute reducing gas to a metallic mirror deposit.

ln producing the metallic mirror layer any reducing gas sufficientlyreductive to reduce the specific metallic oxide to the metal can beused. For example, to produce an iron mirror,an exterior iron oxidelayer is reduced, in accordance with this invention, using hydrogen,carbon monoxide, methane, or the like. lt is preferred that the sweepatmosphere in which the reducing gas is transported be nitrogen. lfpassivation is required, e.g., with an iron mirror, carbon dioxide sweepover the coating or deposition is adequate for at least temporaryprotection. A silicon dioxide layer or other protective oxide layer isalso eminently satisfactory. A preferred method for providing a silicondioxide overcoat for a mirror layer, in accordance with this invention,includes vaporizing tetraethoxysilanol in a vaporizer with an inert gassweep, and in a second dilute sweep, adding oxygen, and admixing thesestreams under the conditions described in Example I herein.

To provide an electro-optical layer, tetraethyl lead can be vaporized ina high velocity inert gas sweep through vaporizer and low concentrationsof hydrogen sulfide provided in the second sweep gas. Silver chloride orcopper formate can be vaporized at an extremely low rate, in a secondvaporizer, as described hereinbefore, to deposit minute levels of silveror copper dopant in the lead sulfide layer. The resulting silver orcopper doped lead sulfide can function as an optical sensor providingelectrical readout.

The table is presented herein to illustrate the farreachingapplicability of the method of this invention, with respect to elementalconstitutents of the layer compound. In the table, illustrative volatilecompounds or elements are set forth, and arranged in alphabetical orderaccording to the chemical symbol for the element involved. Alltemperatures are suggested temperatures and are provided only for thepurpose of illustration, and not for limitation. In the Table, Dop. isan abbreviation for Dopant, Min, for Mirror, and Trans. for transparentlayer. A Yes under the respective column heading indicates the materialset forth is readily used in accordance with this invention to provide adopant, opaque layer (mirror) or transparent layer, respectively.

The entire process of this invention is preferably carried on atsubstantially atmospheric pressure. However, it is not essential thatall portions of the system be maintained at precisely atmosphericpressure. In fact, it is highly desirable to provide the input gases ata pressure somewhat above atmospheric pressure, e.g., 5-l 5 psig, sothat the flow rates through the system can be maintained at constantvalue. Also, to provide a higher TABLE Metal Material Being Vap. DepositFormula Metal Name Vaporized Temp. Temp. Dop. Mir Trans.

Ag Silver Silver Chloride 400 300 Yes Yes Al Aluminum Al l 50 200 YesYes As Arsenic Arsine (AsH gas 200 Yes Yes Chloridc(AsCl 30 200 Yes YesAv Gold (C H P-AuCl 30 I Yes Yes Be Beryllium diethyl beryllium, 30 200Yes Yes dimethyl, I00 200 Yes Yes ditert butyl 30 200 Yes Yes Bi BismuthBiH gas 200 Yes Yes BiCl; 200 200 Yes Yes 8 Boron lhH gas 300 Yes Yes CdCadmium Metal 400 Cond Yes Co Cobalt Co(CO) 30 200 Yes Yesacetylacetonate 30 200 Yes Yes Cr Chromium dicumene chromium 50 200 YesYes Yes acetyl acetonate 100 250 Yes Yes Yes ehromyl chloride 30 300 YesYes Yes Cr(CO), 30 300 Yes Yes Yes Cs Cesium metal 400 Cond Yes 300 CuCopper Formate I00 300 Yes Yes Yes acetyl acetonate I00 300 Yes Yes YesFe lron Fe(CO) 30 200 Yes Yes acetylacetonate 300 200 Yes Yes GeGermanium GcH, gas 300 Yes Yes Yes Gel: 30 300 Yes Yes Yes Ge(OC H,) C H400 Yes Yes Yes Hg Mercury metal 200 100 cond. I00

diethyl mercury 50 200 Yes No Yes I lodinc lodine(l,) I00 40-60 Yes KPotassium metal 300 Cond. Yes Mg Magnesium metal 500 Cond. Yes MnManganese Dicyclopentadienyl 30 200 Yes Yes Mo Molybdenum Mo(CO) 200 YesYes Ni Nickel Ni(CO) 30 200 Yes Yes acetylacetonate I00 300 Yes Yes OsOsmium 0s(C0),Cl, I00 300 Yes Yes P Phosphorous metal 200 I50 Yes PHggas 200 Yes Yes Pb Lead tetraethyl 30 300 Yes Yes tetramethyl 30 300 YesYes Rb Rhubidium metal 400 Cond. Yes Rh Rhodium RhCl 03 CO 50 200 YesYes S Sulfur Sulfur 300 Cond. Yes Sb Antimony SbCl 100 500 Yes Yes YesSbH gas lOO Yes Yes Yes Se Selenium Sell gas 300 Yes Yes Yes Si Siliconmetal 500 Cond. Yes

Si(OC,H 30 300 Yes Sn Tin tetramethyl 60 200 Yes Yes tetraethyl 30 200Yes Yes triethylchloride 30 200 Yes Yes Te Tellurium metal 500 Cond. YesTi Titanium tetraethyl 30 300 Yes Yes We Tungsten W(CO),, 50 200 Yes YesZn Zinc metal 500 Cond. Yes

50 200 Yes diethyl mass transfer rate, pressures higher than atmosphericpressure can be employed, providing the essential concentrationlimitations are observed though elevated pressure is not necessary. Forexample, pressures in the range 0.1 to 4 atmospheres are eminentlysatisfactory.

From a consideration of the deposition temperatures set forth in thetable herein it is apparent that the deposition temperatures useful inaccordance with this invention are preferably in the range 40 to 400C.The more preferred temperatures range from about 100 to 280C inclusive.Higher deposition temperatures are sometimes useful. It is importantthat the dilute gas stream moving towards chamber 100 be maintained attemperatures below deposition temperatures when a chemical reaction isinvolved in the deposition mechanism. Those embodiments in which theprimary and secondary streams carry first and second reactants whichresult in a third material in the layer, e.g., as in the detailedillustrated example herein, are of this type. However, when condensationis involved, e.g., when elemental metal is vaporized and condensed, itis imat least at a reduced rate if it is intended to change over fromone deposition layer to another, in order to reduce the time in whichthe transition zones, e.g., 30, 32, 34, 36, are being laid down.

Also, although the detailed example set forth above is a preferredembodiment in which relatively narrow transition zones are automaticallylaid down, it is not essential that in all instances such transitionzones be laid down. For example, after the required depth of a layer,e.g., 18, is deposited, the entire system could be flushed with an inertsweep gas, e.g., C0,, or N (or operated with valves 66, 68 closed whentrap 114 is operating and recycle mode prevails) and the seconddeposition material, e.g., chromium carbonyl, with low level of oxygen,can be introduced into chamber 100 in a dilute sweep flow with theresult that no iron amyl acetate is present during deposition of thesecond layer, e.g., chromium oxide. Such an embodiment provides sharpdemarcation between the respective iron oxide and chromium oxide layers.However, as set forth above, it is preferred that the operation of theapparatus. of this invention be as described since this provides therelatively narrow transition zones 30, 32, 34, 36 which, for somepurposes, are believed to be highly desirable.

In addition, it is within the overall scope of this invention that themagnitude of zones 30, 32, 34, 36 can be increased by providing a longerperiod of time in which several deposition materials are being admittedsimultaneously to manifold 64, e.g., through both conduits 60, 62, intheexample. Such an embodiment in which several materials are beingvaporized simultaneously requires careful'control of vaporizer inputrates in order to assure a high degree of reproductivity from batch tobatch, however. Since the flow rates set forth in the detailed exampleherein are constant, and since a given apparatus will be constant withrespect to its gas-occupied volume and other structural dimensions,controlling the other parameters, i.e., time, and temperature, providesfor highly reproducible dimensions of layers and transition zones.Controlling the period of time in which the deposition material isadmitted to manifold 64 effectively and reproducibly controls themagnitude of the corresponding layer being laid down on lenseslO, givenconstant temperature of substrate from layerto layer.

The substrates which can be used in accordance with this inventioninclude glass, ceramic, and metal, e.g., stainless steel, as well asplastics, e.g., teflon, phenolics, etc., and the like. When plasticsubstrates are used, it is preferred that they be selected from theclass of plastics known as thermosets.

The method of this invention provides uniform layers regardlessofcontour, shape, or line-of-sight accessibility of the substrate surfaceand regardless of number of substrates being processed. The method ofthis invention is likewise singularly beneficial in depositing minutemicroscopic patterns, e.g., microminiature patterns, on a substrate. Inthis regard, this invention is not directed to any particular method ofmasking or shielding the substrate whereby a particular pattern can belaid down. It is preferred, however, that photographyrelated techniquesbe employed to develop masks or shields on the substrate. Thecombination of the conventional photo-developed pattern generationtechnique with the dilute sweep layer deposition method of thisinvention, produces a new dimension in manufacture of microminiaturepatterned layers involving no manual manipulations relating to theproduction of the layer design on the substrate, only thosemanipulations involving handling of the substrate itself. Hence theresulting layers are deposited in patterns which are extremelyclean-edged even under high magnification.

Thus, it will be apparent from aconsideration of the foregoingdisclosure that this invention provides a substantial advance in the artof simultaneously manufacturing large numbers of layered products, e.g.,selectively deposited patterns, optical filters, such as di- 14 chroic'filters, and for simultaneously depositing such layers on all surfacesof the products unless those surfaces are appropriately shielded.

It will also be apparent from the foregoing that the nature of theapparatus required is very similar to that used in ordinary chemicalmanufacturing processes, particularly vapor phase processes, and thatthe nature of the regulation and control of the process is such that itreadily lends itself to automatic control and other highly automatedprocedures. Moreover, the level of technical skill required by anoperator is low, and yet in spite of this high reproducibility and ahigh level of process control is conveniently practicaL' Also, since thedeposition does not depend on a lineof-sight travel of the materialbeing laid down, it is found that the coating being laid down on lenses10 in accordance with this invention is highly uniform regardless of theshape of the face of the substrate being coated.

I claim:

1. A method of depositing a micro-thin opaque or transparent layer on asubstrate comprising: maintaining said substrate at a depositiontemperature between [00C and 300C; forming a dilute gaseous mixture ofvapor of a first metal-containing reactant in an inert gas stream,forming a second gaseous mixture comprising vapor of a second reactantin an inert gas stream, admixing said first and second mixtures, andcontacting the resulting admixture in a high velocity stream with saidsubstrate while it is at said deposition temperature at a pressure inthe range 0.1 to 4 atmospheres, the total concentration of the reactantsin the resulting admixture being less than 5 percent v/v and continuingsaid contacting until said layer is formed on said substrate.

2. The method of claim I in which said contacting takes place at atemperature in the range l00280C., inclusive.

3. The method of claim 1 in which the first reactant is a volatileorgano-metallic compound and the second reactant is a member selectedfrom .the group consisting of oxygen and hydrogen sulfide.

4. A method of claim 1 in which the product is a photoelectric elementand in which the resulting gaseous admixture also includes lowconcentration of a dopant in a concentration less than 0.1 percent v/v.

5. The method of claim 1 in which the substrate is glassfiber.

6. A method of depositing micro-thin oxide layer on a substratecomprising: sweeping a substrate which is maintained at a temperaturebetween l00280C with a sweep gas containing an organo-metallic compoundat a concentration less than 5 percent v/v in an inert carrier gastherein, said gas sweep containing oxygen at a concentration less than0.1 percent v/v, and continuing said sweeping for a period of timesufficient to form said layer on said substrate.

7. A method of making an opaque film on a substrate comprising: forminga micro-thin oxide layer on the substrate, by a method comprisingmaintaining the substrate at a deposition temperature between C to 300C,sweeping said substrate with a dilute gaseous mixture of ametal-containing vaporizable material, and oxygen in an inert carriergas stream, said material and oxygen being present in the inert carriergas stream in a total concentration not exceeding 5 percent v/v, saidsweeping phase taking place at a pressure between 0.1 and 4 atmospheres;and continuing said sweeping for a period of time until said micro-thinoxide layer is formed on said substrate; heating the resulting substrateto a temperature in the range l280C and sweeping the thus heatedsubstrate with an inert gas carrier containing a reducing reactant in anamount less than percent v/v therein.

8. A method of manufacturing an optical filter which includes a multiplelayer light filtering coating on the surface of an optical substrate,which method comprises the steps of:

l. placing the optical substrate in a vented chamber having a relativelylarge volume;

2. maintaining the optical substrate at an elevated temperature between100C and 300C;

3. sweeping the atmosphere from the chamber with an inert gas;

4. Continuously introducing into the chamber a first dilute gaseouscoating mixture including at least one gaseous metal-containing materialand a second reactant in an inert carrier gas, said mixture beingcapable of depositing at said elevated temperature on said substrate afilm containing a first metal compound while continuously venting gasfrom said chamber, and continuing the continuous introducing and ventingof step 4 for a period of time sufficient for a first layer to form onsaid substrate; and

5. introducing into the chamber a second gaseous coating mixtureincluding at least one gaseous metal-containing material and a thirdreactant in an inert carrier gas, said second mixture being capable ofdepositing at said elevated temperature a film containing a second metalcompound, thereby gradually reducing the concentration of said firstcoating mixture, while increasing the concentration of said secondcoating mixture, wherein the total concentration of saidmetal-containing materials and said second reactants in said coatingmixture in steps 4 and 5 is less than 5 percent v/v while continuouslyventing gas from said chamber; and continuing the continuous introducingand venting of step 5 for a period of time sufficient for a second layerto form on the first layer.

9. A method of manufacturing multiple layer optical filters comprisingthe steps of:

forming a first dilute gaseous mixture of a first metallic compound in alarge amount of inert carrier gas;

admixing with said first gaseous mixture a gaseous member selected fromthe group H 5, Asl-l PH NH;,, and H Te, to provide a coating-gas stream;

said first metallic compound being reactive with said gaseous member todevelop a layer on said substrate; and

moving said coating gas stream over a surface to be coated, said surfacebeing at a temperature in the range from 100C to 280C, wherein the totalconcentration of said compound and said member in said stream is 5percent v/v or less, said moving continuing until an optical filterlayer is formed on said substrate.

10. A method of manufacturing dichroic filters comprising the steps of:

heating filter substrates in a coating chamber to a temperature in therange l00-280C;

said chamber being maintained at substantially atmospheric pressure;

forming a first dilute gaseous admixture of a first reactive metalliccompound and chemically inert sweep gas; admixing with said firstadmixture a relatively small amount of a second reactive compound, whichsecond reactive compound is characterized as coacting with said firstadmixture to deposit a first filter layer material on said heatedsubstrate, the mixture resulting being a second gaseous mixture;

sweeping said second mixture over the heated substrates by dischargingthe second mixture into the coating chamber and continuously venting gasfrom the coating chamber;

forming a third gaseous admixture of a vaporizable metallic compound andinert carrier gas, admixing the third mixture thoroughly with arelatively small amount of fourth reactive gaseous compoundcharacterized by its ability to co-act with said third mixture to form asecond filter layer material, on said first filter layer material, theadmixing of said fourth compound with said third mixture resulting in afifth gaseous mixture; and sweeping the fifth gaseous mixture over thesubstrate by discharging the fifth gaseous mixture into the coatingchamber and continuously venting the chamber, wherein the totalconcentration of reactants in any substratecontacting gas stream is 5percent v/v or less, said sweeping continuing in each instance, until arespective filter layer is deposited.

11. A method of selectively depositing a micro-thin layer on a substratecomprising: maintaining the substrate at an elevated temperature betweenC and 300C; contacting said substrate with a dilute gaseous mixturecontaining a deposit precursor consisting of a metal-containing materialin vapor form and a second reactive compound characterized as co-actingwith said material to form a first filter layer on the heated substratein a concentration not exceeding 5 percent v/v, and continuing thecontacting for a period of time sufficient for a layer to be depositedon said substrate, said depositing taking place through stencil meansfor preventing deposition in nonselected areas, and for depositing saidlayers in selected areas.

12. A method of depositing a micro-thin optical layer on a substratecomprising: maintaining said substrate at a deposition temperaturebetween 100C and 300C; sweeping said substrate with a sweep of a dilutegaseous mixture containing a depositprecursor comprising ametal-containing vaporizable material in vapor form and a secondreactant capable of reacting with the precursor to produce an opticallyactive layer on said substrate, said reactants being in an inert carriergas stream in which the total concentration of deposit precursor andsecond reactant does not exceed 5 percent v/v; and continuing saidsweeping for a period of time sufficient to form an optically activelayer on said substrate.

13. The method of claim 12 in which said sweeping takes place at apressure between 0.l and 4 atmospheres, inclusive.

14. The method of claim 12 in which a gaseous mixture includes aplurality of reactants which produce a layer having a composition whichis different from any of the reactants, and in which gaseous mixtures aconcentration of no one reactant is in excess of l percent v/v.

15. A method of forming a uniform oxide coating on a substratecomprising: maintaining said substrate at a deposition temperaturebetween 100C and 300C; sweeping said substrate with a dilute gaseousmixture of a metal-containing vaporizable material, and oxygen in aninert carrier gas stream, said material and oxygen being present in saidinert carrier gas stream in a total concentration not exceeding percentv/v, said sweeping taking place at a pressure between 0.1 and 4atmospheres; and continuing said sweeping for a period of time until ametal oxide layer is formed on said substrate.

16. The method of claim 15 in which gaseous mixture the concentration ofno one reactant is in excess of 1 percent v/v.

17. The method of claim 15 in which the metal containing material isselected from the group consisting of silver chloride, Al l arsenicchloride, arsine (C H P-AuCl, dimethyl beryllium, ditert butylberyllium, Bil-l BiCl B H cadmium metal, cobalt acetylacetonate, Co(CO)dicumene chromium, chromium acetyl acetonate, chromyl chloride, Cr(CO)cesium metal, copper formate,copper acetyl acetonate, Fe( CO) ironacetylacetonate, iron amyl-acetonate, GeH,,, Gel mercury metal, diethylmercury, iodine (l potassium metal, magnesium metal, manganesedicyclopentadienyl, Mo(CO) Ni(CO) nickel acetylacetonate, Os(CO) Clphosphorous, Pl-l tetraethyl lead, tetramethyl lead, rhubidium metal,RhCl O-S CO,

sulfur, SbCl SbH SeH silicon metal, Si(OC l-l tetramethyl tin,tetraethyl tin, tin triethylchloride, tellurium metal, tetraethyltitanium, W(CO) zinc metal, diethyl zinc, and diethyl beryllium.

18. A method of depositing an optically active layer on a substratecomprising: maintaining substrate at a deposition temperature between Cand 300C; sweeping said substrate with a sweep of dilute gaseous mixturecontaining a primary and secondary reactant in an inert carrier gasstream wherein said primary reactant is a metal-containing vaporizablematerial, and wherein said secondary reactant is a member selected fromthe group consisting of oxygen, hydrogen sulfide, hydrogen selenide,hydrogen telluride, ammonia, arsine, and phosphine, and wherein saidreactants are present in a concentration not exceeding 5 percent v/v,and continuing said sweeping for a period of time sufficient to form anoptically active coating on said substrate.

19. The method of claim 18 wherein said primary reactant is a memberselected from the group consisting of silver chloride, A1 1 arsenicchloride, arsine, (C H P'AuCl, dimethyl beryllium, diethyl beryllium,ditert butyl beryllium, BiH BiCl B H cadmium metal, cobaltacetylacetonate, Co(CO) dicumene chromium, chromium acetyl acetonate,chromyl chloride, Cr(CO) cesium metal, copper formate, copper acetylacetonate, Fe(CO) iron acetylacetonate, iron amyl-acetonate, GeH Gelmercury metal, diethyl mercury, iodine (l potassium metal, magnesiummetal, manganese dicyclopentadienyl, Mo(CO) Ni(- CO) nickelacetylacetonate, Os(CO) Cl phosphorous, PH tetraethyl lead, tetramethyllead, rhubidium metal, RhCl O'3 CO, sulfur, SbCl SbH SeH silicon metal,Si(OC H tetramethyl tin, tetraethyl tin, tin triethylchloride, telluriummetal, tetraethyl titanium,

W(CO) zinc metal, and diethyl zinc.

2. maintaining the optical substrate at an elevated temperature between100*C and 300*C;
 2. The method of claim 1 in which said contacting takesplace at a temperature in the range 100-280*C., inclusive.
 3. The methodof claim 1 in which the first reactant is a volatile organo-metalliccompound and the second reactant is a member selected from the groupconsisting of oxygen and hydrogen sulfide.
 3. sweeping the atmospherefrom the chamber with an inert gas;
 4. Continuously introducing into thechamber a first dilute gaseous coating mixture including at least onegaseous metal-containing material and a second reactant in an inertcarrier gas, said mixture being capable of depositing at said elevatedtemperature on said substrate a film containing a first metal compoundwhile continuously venting gas from said chamber, and continuing thecontinuous introducing and venting of step 4 for a period of timesufficient for a first layer to form on said substrate; and
 4. A methodof claim 1 in which the product is a photoelectric element and in whiChthe resulting gaseous admixture also includes low concentration of adopant in a concentration less than 0.1 percent v/v.
 5. The method ofclaim 1 in which the substrate is glass fiber.
 5. introducing into thechamber a second gaseous coating mixture including at least one gaseousmetal-containing material and a third reactant in an inert carrier gas,said second mixture being capable of depositing at said elevatedtemperature a film containing a second metal compound, thereby graduallyreducing the concentration of said first coating mixture, whileincreasing the concentration of said second coating mixture, wherein thetotal concentration of said metal-containing materials and said secondreactants in said coating mixture in steps 4 and 5 is less than 5percent v/v while continuously venting gas from said chamber; andcontinuing the continuous introducing and venting of step 5 for a periodof time sufficient for a second layer to form on the first layer.
 6. Amethod of depositing micro-thin oxide layer on a substrate comprising:sweeping a substrate which is maintained at a temperature between100-280*C with a sweep gas containing an organo-metallic compound at aconcentration less than 5 percent v/v in an inert carrier gas therein,said gas sweep containing oxygen at a concentration less than 0.1percent v/v, and continuing said sweeping for a period of timesufficient to form said layer on said substrate.
 7. A method of makingan opaque film on a substrate comprising: forming a micro-thin oxidelayer on the substrate, by a method comprising maintaining the substrateat a deposition temperature between 100*C to 300*C, sweeping saidsubstrate with a dilute gaseous mixture of a metal-containingvaporizable material, and oxygen in an inert carrier gas stream, saidmaterial and oxygen being present in the inert carrier gas stream in atotal concentration not exceeding 5 percent v/v, said sweeping phasetaking place at a pressure between 0.1 and 4 atmospheres; and continuingsaid sweeping for a period of time until said micro-thin oxide layer isformed on said substrate; heating the resulting substrate to atemperature in the range 100-280*C and sweeping the thus heatedsubstrate with an inert gas carrier containing a reducing reactant in anamount less than 5 percent v/v therein.
 8. A method of manufacturing anoptical filter which includes a multiple layer light filtering coatingon the surface of an optical substrate, which method comprises the stepsof:
 9. A method of manufacturing multiple layer optical filterscomprising the steps of: forming a first dilute gaseous mixture of afirst metallic compound in a large amount of inert carrier gas; admixingwith said first gaseous mixture a gaseous member selected from the groupH2S, AsH3, PH3, NH3, and H2Te, to provide a coating-gas stream; saidfirst metallic compound being reactive with said gaseous member todevelop a layer on said substrate; and moving said coating gas streamover a surface to be coated, said surFace being at a temperature in therange from 100*C to 280*C, wherein the total concentration of saidcompound and said member in said stream is 5 percent v/v or less, saidmoving continuing until an optical filter layer is formed on saidsubstrate.
 10. A method of manufacturing dichroic filters comprising thesteps of: heating filter substrates in a coating chamber to atemperature in the range 100*-280*C; said chamber being maintained atsubstantially atmospheric pressure; forming a first dilute gaseousadmixture of a first reactive metallic compound and chemically inertsweep gas; admixing with said first admixture a relatively small amountof a second reactive compound, which second reactive compound ischaracterized as co-acting with said first admixture to deposit a firstfilter layer material on said heated substrate, the mixture resultingbeing a second gaseous mixture; sweeping said second mixture over theheated substrates by discharging the second mixture into the coatingchamber and continuously venting gas from the coating chamber; forming athird gaseous admixture of a vaporizable metallic compound and inertcarrier gas, admixing the third mixture thoroughly with a relativelysmall amount of fourth reactive gaseous compound characterized by itsability to co-act with said third mixture to form a second filter layermaterial, on said first filter layer material, the admixing of saidfourth compound with said third mixture resulting in a fifth gaseousmixture; and sweeping the fifth gaseous mixture over the substrate bydischarging the fifth gaseous mixture into the coating chamber andcontinuously venting the chamber, wherein the total concentration ofreactants in any substrate-contacting gas stream is 5 percent v/v orless, said sweeping continuing in each instance, until a respectivefilter layer is deposited.
 11. A method of selectively depositing amicro-thin layer on a substrate comprising: maintaining the substrate atan elevated temperature between 100*C and 300*C; contacting saidsubstrate with a dilute gaseous mixture containing a deposit precursorconsisting of a metal-containing material in vapor form and a secondreactive compound characterized as co-acting with said material to forma first filter layer on the heated substrate in a concentration notexceeding 5 percent v/v, and continuing the contacting for a period oftime sufficient for a layer to be deposited on said substrate, saiddepositing taking place through stencil means for preventing depositionin nonselected areas, and for depositing said layers in selected areas.12. A method of depositing a micro-thin optical layer on a substratecomprising: maintaining said substrate at a deposition temperaturebetween 100*C and 300*C; sweeping said substrate with a sweep of adilute gaseous mixture containing a deposit precursor comprising ametal-containing vaporizable material in vapor form and a secondreactant capable of reacting with the precursor to produce an opticallyactive layer on said substrate, said reactants being in an inert carriergas stream in which the total concentration of deposit precursor andsecond reactant does not exceed 5 percent v/v; and continuing saidsweeping for a period of time sufficient to form an optically activelayer on said substrate.
 13. The method of claim 12 in which saidsweeping takes place at a pressure between 0.1 and 4 atmospheres,inclusive.
 14. The method of claim 12 in which a gaseous mixtureincludes a plurality of reactants which produce a layer having acomposition which is different from any of the reactants, and in whichgaseous mixtures a concentration of no one reactant is in excess of 1percent v/v.
 15. A method of forming a uniform oxide coating on asubstrate comprising: maintaining said substrate at a depositiontemperature between 100*C and 300*C; sweeping said substrate with adilute gaseous mixture of a metal-containing vaporizable material, andoxygen in an inert carrier gas stream, said material and oxygen beingpresent in said inert carrier gas stream in a total concentration notexceeding 5 percent v/v, said sweeping taking place at a pressurebetween 0.1 and 4 atmospheres; and continuing said sweeping for a periodof time until a metal oxide layer is formed on said substrate.
 16. Themethod of claim 15 in which gaseous mixture the concentration of no onereactant is in excess of 1 percent v/v.
 17. The method of claim 15 inwhich the metal containing material is selected from the groupconsisting of silver chloride, Al2I6, arsenic chloride, arsine(C4H9)3P.AuCl, dimethyl beryllium, ditert butyl beryllium, BiH3, BiCl3,B2H6, cadmium metal, cobalt acetylacetonate, Co(CO)4, dicumene chromium,chromium acetyl acetonate, chromyl chloride, Cr(CO)6, cesium metal,copper formate,copper acetyl acetonate, Fe(CO)5, iron acetylacetonate,iron amyl-acetonate, GeH4, GeI3, mercury metal, diethyl mercury, iodine(I2), potassium metal, magnesium metal, manganese dicyclopentadienyl,Mo(CO)6, Ni(CO)4, nickel acetylacetonate, Os(CO)3Cl3, phosphorous, PH3,tetraethyl lead, tetramethyl lead, rhubidium metal, RhCl2O.3 CO, sulfur,SbCl3, SbH3, SeH2, silicon metal, Si(OC2H5)4, tetramethyl tin,tetraethyl tin, tin triethylchloride, tellurium metal, tetraethyltitanium, W(CO)6, zinc metal, diethyl zinc, and diethyl beryllium.
 18. Amethod of depositing an optically active layer on a substratecomprising: maintaining substrate at a deposition temperature between100*C and 300*C; sweeping said substrate with a sweep of dilute gaseousmixture containing a primary and secondary reactant in an inert carriergas stream wherein said primary reactant is a metal-containingvaporizable material, and wherein said secondary reactant is a memberselected from the group consisting of oxygen, hydrogen sulfide, hydrogenselenide, hydrogen telluride, ammonia, arsine, and phosphine, andwherein said reactants are present in a concentration not exceeding 5percent v/v, and continuing said sweeping for a period of timesufficient to form an optically active coating on said substrate. 19.The method of claim 18 wherein said primary reactant is a memberselected from the group consisting of silver chloride, Al2I6, arsenicchloride, arsine, (C4H9)3P.AuCl, dimethyl beryllium, diethyl beryllium,ditert butyl beryllium, BiH3, BiCl3, B2H6, cadmium metal, cobaltacetylacetonate, Co(CO)4, dicumene chromium, chromium acetyl acetonate,chromyl chloride, Cr(CO)6, cesium metal, copper formate, copper acetylacetonate, Fe(CO)5, iron acetylacetonate, iron amyl-acetonate, GeH4,GeI3, mercury metal, diethyl mercury, iodine (I2), potassium metal,magnesium metal, manganese dicyclopentadienyl, Mo(CO)6, Ni(CO)4, nickelacetylacetonate, Os(CO)3Cl3, phosphorous, PH3, tetraethyl lead,tetramethyl lead, rhubidium metal, RhCl2O.3 CO, sulfur, SbCl3, SbH3,SeH2, silicon metal, Si(OC2H5)4, tetramethyl tin, tetraethyl tin, tintriethylchloride, tellurium metal, tetraethyl titanium, W(CO)6, zincmetal, and diethyl zinc.